Any missed opportunities from a storytelling perspecive?

With the quick pace of the game's main story it will naturally happen that some story aspects will not get the chance to be fully explored. As the story progresses in a certain direction it can be difficult or impossible to ever get the chance to explore these things properly, whether it be a side story, a faction, a character or even world location. Are there any stories within the game that were either left as loose ends or brushed through really quickly in order to advance the main story that you wish you would have had more time working on and really dig into?